Of the 11 million gallons of crude oil that bled from the stranded Exxon Valdez on the night of March 23, 1989, more than 21,000 gallons (79,500 liters) remain, tucked into isolated coves and underneath the sand.

"The damage that [the spill] created is something beyond anyone's imagination," said Michel Boufadel, Temple University's Civil and Environmental Engineering chair, who has just completed research on why the Exxon Valdez oil has persisted.